Do, re and mi are the first three syllables of solfege, the system music teachers have long used to teach pitch and scales, which is why the sequence feels familiar even to people who have never studied music formally. Online, short vocal versions circulate as standalone clips because the rising pattern is easy to recognise, easy to place and instantly signals that something musical is about to happen. Creators keep returning to it for intros, jokes and transitions, and its simplicity means it still works in memes and short-form videos years after similar trends have faded.